Yes the dev would need access to the Keys to effectively open the update pup edit it, the resign it again, keeping the update method the same as Sony are now using.
I also believe sony would of implemented a hash key to test the integrity of is new firmware before it updates, making it almost imposable to know this key or create it with a firmware modifier regardless of having the 3.66 keys or not.
But no this dev does not have the 3.66 keys needed to fully exploit the ps3 with firmware above 3.56.
Some thing I forgot to add was remember to remove the wan access from the ps3 your flashing, your lans ok but not your wan.
This will almost certainly stop you installing cfw on a ps3 9 times out of 10 because it still checks the net 1st, just before it starts flashing the firmware.